Into the Looking Glass: Cryogenic Extremes
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|Courtesy of NASA|
The Webb telescope has 18 mirrors, each of which is tested twice in the Center's X-ray and Cryogenic Facility to ensure that the mirror will maintain its shape in a space environment — once with bare polished beryllium and then again after a thin coating of gold is applied.
The cryogenic test gauges how each mirror changes temperature and shape over a range of operational temperatures in space. This helps predict how well the telescope will image infrared sources.
The mirrors are designed to stay cold to allow scientists to observe the infrared light they reflect using a telescope and instruments optimized to detect this light. Warm objects give off infrared light, or heat. If the Webb telescope mirror is too warm, the faint infrared light from distant galaxies may be lost in the infrared glow of the mirror itself. Thus, the Webb telescope's mirrors need to operate in a deep cold or cryogenic state, at around -379 degree Fahrenheit.